Lake Tahoe () is a freshwater lake in the Sierra Nevada of the Western United States, straddling the border between California and Nevada. Lying at above sea level, Lake Tahoe is the largest alpine lake in North America, and at it trails only the five Great Lakes as the largest by volume in the United States. Its depth is , making it the second deepest in the United States after Crater Lake in Oregon ().
The lake was formed about two million years ago as part of the Lake Tahoe Basin, and its present extent was shaped during the ice ages. It is known for the clarity of its water and the panorama of surrounding mountains on all sides. The area surrounding the lake is also referred to as Lake Tahoe, or simply Tahoe; its English name is derived from its Washo name, ."The Washoe People" Past and Present More than 75% of the lake's watershed is national forest land, covered by the Lake Tahoe Basin Management Unit of the United States Forest Service.
Lake Tahoe is a major tourist attraction in both Nevada and California. It is home to winter sports, summer outdoor recreation, and scenery enjoyed throughout the year. Snow and ski resorts are a significant part of the area's economy and reputation. The Nevada side also offers several lakeside casino resorts, with highways providing year-round access to the entire area.
Toponym The name for Lake Tahoe derives from the Washo word for the lake, , meaning 'the lake.' Even though is used in the names of other lakes with modifiers (for example, for Pyramid Lake, meaning 'trout lake'), it often is used without a modifier to refer to Lake Tahoe. This may be because of Tahoe's importance to Washo culture.Natalie E. Davenport (2019). "Naming, Remembering, and Experiencing We' lmelt' iʔ [northern Washoe] Cultural Spaces in Wa she shu It Deh [Washoe Land]". ScholarWorks, University of Nevada, Reno. Accessed 1 Jan 2023. pp. 194, 329. https://scholarworks.unr.edu/bitstream/handle/11714/6780/Davenport_unr_0139D_13067.pdf
Geography
Lake Tahoe is the second deepest lake in the U.S., with a maximum depth of , trailing Oregon's Crater Lake at . Tahoe is the 17th deepest lake in the world, and the sixth deepest in average depth. It is about long and wide and has of shoreline and a surface area of . The lake is so large that its surface is noticeably convex due to the curvature of the Earth. At lake level the opposing shorelines are below the horizon at its widest parts; by nearly at its maximum width, and by some along its length. Visibility may vary somewhat with atmospheric refraction; when the air temperature is much greater than the lake temperature, looming may occur where the lake surface or opposing shoreline is lifted above the horizon. Fata Morgana may be responsible for Tahoe Tessie sightings.
Approximately two-thirds of the shoreline is in California. The south shore is dominated by the lake's largest city, South Lake Tahoe, California, which adjoins the town of Stateline, Nevada, while Tahoe City, California, is located on the lake's northwest shore. Kings Beach, California, and Incline Village, Nevada, anchor the lake's north shore. Although highways run within sight of the lake shore for much of Tahoe's perimeter, many important parts of the shoreline lie within state parks or are protected by the United States Forest Service. The Lake Tahoe Watershed (USGS Huc 18100200) of is the land area that drains to the lake and the Lake Tahoe drainage divide traverses the same general area as the Tahoe Rim Trail.
Lake Tahoe is fed by 63 tributaries. These drain an area about the same size as the lake and produce half its water; the other half is produced by direct precipitation.
The Truckee River is the lake's only outlet, flowing northeast through Reno, Nevada, into Pyramid Lake which has no outlet. It accounts for one third of the water that leaves the lake, the rest evaporating from the lake's surface. Evaporation is thought to account for 40 to 60 percent of the water usage.Friedrich, Katja, et al. "Reservoir Evaporation in the Western United States: Current Science, Challenges, and Future Needs." Bulletin of the American Meteorological Society, vol. 99, no. 1, 2018, p. 169. JSTOR website Retrieved 5 June 2023. The flow of the Truckee River and the height of the lake are controlled by Lake Tahoe Dam at the outlet. The natural rim is at above sea level. The maximum legal limit to which the lake can be allowed to rise in order to store water is at ; a spillway at the dam controls overflow. Around New Year 1996/1997 a Pineapple Express atmospheric river melted snow and caused the lake and river to overflow, inundating Reno and surrounding areas.
Natural history
Geology The Lake Tahoe Basin was formed by vertical motion (normal) faulting. Uplifted blocks created the Carson Range on the east and the main Sierra Nevada crest on the west. Down-dropping and block tilting (half-grabens) created the Lake Tahoe Basin in between. This kind of faulting is characteristic of the geology of the adjoining Great Basin to the east.
Lake Tahoe is the youngest of several extensional basins of the Walker Lane deformation zone that accommodates nearly per year of dextral shear between the Sierra Nevada-Great Valley Block and the North America plate.
Three principal faults form the Lake Tahoe basin: the West Tahoe Fault, aligned between Meyers and Tahoe City, and which is the local segment of the Sierra Nevada Fault, extending on shore north and south of these localities; the Stateline/North Tahoe Fault, starting in the middle of the lake and creating the relief that forms Stateline, NV; and the Incline Village Fault, which runs parallel to the Stateline/North Tahoe Fault offshore and into Incline Village. The West Tahoe Fault appears to be the most active and potentially hazardous fault in the basin. A study in Fallen Leaf Lake, just south of Lake Tahoe, used seafloor mapping techniques to image evidence for paleoearthquakes on the West Tahoe and revealed the last earthquake occurred between 4,100 and 4,500 years ago. Subsequent studies revealed submarine landslides in Fallen Leaf Lake and Lake Tahoe, thought to have been triggered by earthquakes on the West Tahoe fault, and the timing of these events suggests a recurrence interval of 3,000–4,000 years.
Some of the highest peaks of the Lake Tahoe Basin that formed during the process of Lake Tahoe creation are Freel Peak at , Monument Peak at , Pyramid Peak at (in the Desolation Wilderness), and Mount Tallac at . The north shore boasts three peaks at over : Mount Rose at , Mount Houghton at and Relay Peak at . Mt. Rose is a very popular hiking and backcountry skiing destination.
Eruptions from the now-extinct volcano Mount Pluto formed a volcanic dam on the north side. Melting snow filled the southern and lowest part of the basin to form the ancestral Lake Tahoe. Rain and runoff added additional water.
The Sierra Nevada adjacent to Lake Tahoe were carved by scouring glaciers during the Ice Ages, which began a million or more years ago, and retreated ~15,000 years ago at the end of the Pleistocene. The glaciers carved canyons that are today iconic landmarks such as Emerald Bay, Cascade Lake, and Fallen Leaf Lake, among others. Lake Tahoe itself never held glaciers, but instead water is retained by damming Miocene volcanic deposits.
Soils of the basin come primarily from andesitic volcanic rocks and granodiorite, with minor areas of metamorphic rock. Some of the valley bottoms and lower hill slopes are mantled with glacial moraines, or glacial outwash material derived from the parent rock. Sandy soils, rock outcrops and rubble and stony colluvium account for over 70% of the land area in the basin. The basin soils (in the < 2 mm fraction) are generally 65–85% sand (0.05–2.0 mm).
Given the great depth of Lake Tahoe, and the locations of the normal faults in the deepest portions of the lake, modeling suggests that earthquakes on these faults can trigger tsunamis. Wave heights of these tsunamis are predicted to be on the order of in height, capable of traversing the lake in just a few minutes. A massive collapse of the western edge of the basin that formed McKinney Bay around 50,000 years ago is thought to have generated a tsunami/seiche wave with a height approaching .
Climate
Lake Tahoe has a dry-summer continental climate (Dsb in the Köppen climate classification), featuring warm, dry summers and cold winters with heavy snowfall. Mean annual precipitation ranges from over for watersheds on the west side of the basin to about near the lake on the east side of the basin. Most of the precipitation falls as snow between November and April, although rainstorms combined with rapid snowmelt account for the largest floods. There is a pronounced annual runoff of snowmelt in late spring and early summer, the timing of which varies from year to year. In some years, summertime monsoon storms from the Great Basin bring intense rainfall, especially to high elevations on the northeast side of the basin.
August is normally the warmest month at the Lake Tahoe Airport (elevation ) with an average maximum of and an average minimum of . January is the coolest month with an average maximum of and an average minimum of . The all-time maximum of was recorded on July 22, 1988. The all-time minimum of was recorded on December 9, 1972. Temperatures exceed on an average of 2.0 days annually. Minimum temperatures of or lower occur on an average of 231.8 days annually, and minimum temperatures of or lower occur on an average of 7.6 days annually. Freezing temperatures have occurred in every month of the year. (1903–2007 climate data) (30-year climate data)
Ecology
Vegetation in the basin is dominated by a mixed conifer forest of jeffrey pine (Pinus jeffreyi), lodgepole pine (P. contorta), white fir (Abies concolor), red fir (A. magnifica), sugar pine (P. lambertiana), California incense-cedar (Calocedrus decurrens), ponderosa pine (P. ponderosa), and western white pine (P. monticola). The basin also contains significant areas of wet meadows and riparian areas, dry meadows, brush fields (with Arctostaphylos and Ceanothus) and rock outcrop areas, especially at higher elevations. Ceanothus is capable of fixing nitrogen, but mountain alder (Alnus tenuifolia), which grows along many of the basin's streams, springs and seeps, fixes far greater quantities, and contributes measurably to nitrate-N concentrations in some small streams. The beaches of Lake Tahoe are the only known habitat for the rare Lake Tahoe yellowcress (Rorippa subumbellata), a plant which grows in the wet sand between low- and high-water marks. Vegetation in the lake itself formerly consisted of native Chara and Gomphoneis algae and coontail (Ceratophyllum demersum), but the later introduction of curlyleaf pondweed (Potamogeton crispus), Eurasian watermilfoil (Myriophyllum spicatum), and Zygnema and Cladophora algae has transformed the nearshore environment.
Native fish of the lake include Lahontan cutthroat trout (Oncorhynchus clarki henshawi), mountain whitefish (Prosopiurm williamsoni), Lahontan speckled dace (Rhinichthys osculus robustus), Lahontan redside (Rhinichthys egregious), Lahontan Lake tui chub (Siphateles bicolor pectinifer), Tahoe sucker (Catostomus tahoensis), Lahontan mountain sucker (Catostomus platyrhynchus lahontan), and Paiute sculpin (Cottus beldingi). Most of these fish populations have been significantly reduced due to the introduction of nonnative fish, Asian clam (Corbicula fluminea), and mysid shrimp. Competition from introduced fish led cutthroat trout to be completely extirpated from the lake in the early 20th century until reintroduction efforts started in 2019.